One of the most serious hazards to divers is decompression sickness which is commonly known as the bends. The average human body, at sea level, contains about one liter of dissolved nitrogen. For each atmosphere in depth that a diver ascends into the ocean his body will in time absorb an additional liter of nitrogen. The full time required for complete saturation at any particular atmospheric depth is about 24 hours.
The absorption of nitrogen is accomplished by breathing in the higher pressure air. In the lungs the blood absorbs the nitrogen, and as the blood passes throughout the body, tissues will also absorb the nitrogen. Decompression sickness will not occur with a rapid descent into the ocean since the nitrogen is absorbed progressively as the diver breathes. However, when the diver ascends too quickly from an ocean depth the nitrogen within the diver's tissues cannot be passed quickly enough from the tissues to the blood, thence from the blood to the lungs and then exhaled by the diver. The consequence of this situation is that nitrogen bubbles form in the tissues and in the blood which causes pressure on nerves, the damage of delicate tissues, and a blockage of flow of blood to the vital organs. Symptoms may range from skin rash to mild discomfort and pain in the joints and muscles, to paralysis, numbness, hearing loss, vertigo, unconsciousness, and in extreme cases, death.
The treatment of decompression sickness is normally placement of the diver into a decompression chamber. The pressure within the chamber puts the nitrogen bubbles back into solution within the diver's body and allows him time to naturally expel the excess nitrogen through his lungs. In most situations the diver must be transported to a shore based decompression chamber either by the vehicle from which he is diving or by a rescue vehicle. This approach is very time consuming since death may result while the diver is awaiting his arrival at the decompression chamber. Accordingly, research is now being conducted to provide a portable decompression chamber which can be utilized on even small boats for compressing a diver back to an appropriate ocean depth as soon as he is brought aboard the boat. Such a portable decompression chamber is described in a patent to Donald Miller, U.S. Pat. No. 3,729,002.
Since the Miller patent there has been additional research to provide an improved air supply system for the portable decompression chamber. One important consideration is the scrubbing of the air breathed within the chamber so that carbon dioxide is removed. Research at Battelle Laboratories has resulted in the use of a fluid amplifier in the decompression chamber for circulating the air, and a scrubber located exterior the chamber for removing the carbon dioxide. However, the Battelle apparatus does not have the capability of single valve rapid pressurization or exhaust of the chamber, and the location of the scrubber outside the chamber results in heavy construction. Further, the Battelle apparatus has no provision for conserving the use of air from the pressurized air source. Other considerations include removing any vomit of the diver from the chamber and maintaining a desired pressure drop throughout the air supply system. A combination of these advantages has heretofore been unattained.